Systemic sclerosis (SSc; scleroderma) is a complex multisystem autoimmune disease of unknown cause associated with early transient inflammation and vascular injury followed by progressive fibrosis affecting skin and internal organs; most frequently esophagus, kidneys, heart, and lungs (I). Monocytes and activated T lymphocytes dominate the early inflammatory infiltrates. Fibrosis, the characteristic histopathology in patients with SSc, includes increased production of collagen and other extracellular matrix (ECM) components, and accumulation of alpha smooth muscle actin (ASMA) positive myofibroblasts. The progressive fibrosis often leads to organ dysfunction including debilitating esophageal dysfunction and pulmonary fibrosis, the leading cause of death for SSc patients. Available data, while variable, indicate an incidence in the United States of 9 t 19 cases /million/year, and prevalence rates ranging from 28 to 253 cases/million (2). Current therapy is limited, with 10 year survival of 55%. The mechanisms leading to activation of fibroblasts and the subsequent over production of ECM are not clear. The observation (3) that collagen producing, activated fibroblasts are localized adjacent to inflammatory infiltrates supports the notion that leucocytes are involved in initiation of fibrosis early in the course of SSc. Cytokines and growth factors such as transforming growth factor (TGF-Beta) and connective tissue growth factor (CTGF) activate fibroblasts and induce their differentiation to myofibroblasts, leading to accumulation of connective tissue. Because myofibroblasts enhance the stiffness of the ECM, produce profibrotic cytokines, and are resistant to apoptosis, their accumulation in tissue is believed to promote progression of fibrosis. The endocannabinoid system (ECS) is a natural system that plays an important role in the regulation of the CNS and immune system. Ajulemic acid (AJA), a non-psychotropic endocannabinoid mimetic has been shown to be highly effective in models of analgesia, inflammation and most recently fibrotic diseases. Experiments in this proposal are designed to further characterize the efficacy and mechanisms of the anti fibrotic action of AJA in 2 different murine models of scleroderma which differ in the contribution of inflammation and fibrosis to the disease process. We will use these models to determine the specific mechanism by which AJA prevents or suppresses progressive fibrosis in models of scleroderma, with the goal of translating this information into the design of a clinical trial to test AJA in patients with SSc. Successful completion of this proposal will facilitate development of a new class of drug with a potentially new mechanism to treat fibrotic disease in general and scleroderma in particular. PUBLIC HEALTH RELEVANCE: JB Therapeutics has assembled an exceptional scientific team to study the pharmacology and mechanism of action of its novel non-psychotropic cannabinod in the treatment of scleroderma. We have recently obtained in vitro and in vivo proof-of-concept data that ajulemic acid, a non-psychotropic nanomolar CB1/ CB2 agonist is highly effective in preventing skin and lung fibrosis in a mouse bleomycin model of scleroderma and inhibits extracellular matrix production by dermal fibroblasts from patients with scleroderma. JB Therapeutics is the sole owner of the IP around ajulemic acid and its uses, and is planning to advance a twice-a-day formulation into clinical trials for the treatment of patients with scleroderma, a life-threatening disease. The proposed experiments will determine in animal models the efficacy and mechanisms of action responsible for the antifibrotic effects of ajulemic acid (AJA).